BACKGROUND: Selenium removal from aqueous solutions can be a significant industrial problem, particularly in the metallurgical industry. In order to evaluate new reducing agents for this application, the reduction of selenious acid (H2SeO3) species with stannous ions (Sn2+) from weakly acidic sulfate solutions containing 300 mg L-1 of selenium at 23 degrees C was studied. RESULTS: At initial pH values < 1.3 and molar ratio = 2, less than 0.5 mu g L-1 of selenium(IV) remained in solution after reduction. The reductive precipitation reaction started as soon as the stannous ions were added to the selenium-bearing solution and was completed in less than 5 min. The reaction products, characterized using X-ray diffraction, electron microscopy, particle and surface area measurements, X-ray photoelectron spectroscopy and chemical analysis, were composed of approximately equal amounts of tin selenide and tin dioxide. In addition to tin selenide a minor amount of selenium(IV) was found to be removed via adsorption on the tin dioxide formed in situ. Tests with a complex industrial solution also resulted in full and stable selenium precipitation. CONCLUSION: Stannous ions were found to be very effective in removing selenious ions from synthetic and industrial solutions, producing very stable precipitates. Copyright (c) 2012 Society of Chemical Industry